Living polymerization allows for the synthesis of new polymers and oligomers with specialized structures. A number of recent advances have occurred in polymerization by cationic mechanisms to yield living polymers, where it was previously thought that obtaining living characteristics was unlikely, except for a few ring-opening polymerization systems, due to the reactivity or instability of the ions involved.
T. Higashimura and M. Sawamoto; Adv. Polym. Sci., 1984, 62, 50-94, review the attempts at living cationic polymerization of vinyl monomers and state that until recently it was considered "beyond our reach." They teach away from using oxo acids, such as sulfonic acids, because they believe that the acid derived counterions react with the propagating cations and thereby terminate the polymerization. For example, they show in Table 11 that dimer instead of polymer is produced when p-methoxystyrene is reacted with either CH.sub.3 SO.sub.3 H or CF.sub.3 SO.sub.3 H. They disclose the use of an HI/I.sub.2 initiating system to polymerize isobutyl vinyl ether in n-hexane. They claim this polymerization system to be the first example of living cationic polymerization of vinyl compounds.
M. Miyamoto, M. Sawamoto, and T. Higashimura; Macromol., 1984, 17, 265-268, show that living polymerization of isobutylvinyl ether using HI/I.sub.2, I.sub.2, or HI as initiators, does not occur in a polar solvent such as CH.sub.2 Cl.sub.2.
S. Aoshima and T. Higashimura; Polym. Bull., 1986, 15, 417-423, disclose the use of esters as Lewis base modifiers for EtAlCl.sub.2. These systems are used as initiators for the living cationic polymerization of vinyl ethers.
T. Higashimura, Y. Kishimoto, and S. Aoshima, Polym. Bull., 1987, 18, 111-115, disclose the use of an EtAlCl.sub.2 /dioxane (basic compound) initiating system for the living cationic polymerization of vinyl monomers. A small amount of water is added to the initiating system.
R. Faust and J. P. Kennedy; Polym. Bull., 1986, 15, 317-323, describe the living carbocationic polymerizations of isobutene using initiating complexes of organic esters with Lewis acids.
EP 206, 756, discloses the use of complexes of Lewis acids and organic acids or esters as catalysts for the living polymerization of olefins and diolefins.
JP J6 0228-509, discloses the preparation of polyalkenyl ethers by living polymerization using as catalysts iodine and optionally HI.
U. S. Pat. No. 4,393,199 discloses a method of polymerizing monomers capable of cationic polymerization by using an adduct consisting of a preinitiator precursor and a catalyst, to react with the monomer and produce a polymer of low polydispersity.
U. S. Pat. No. 4,696,988 discloses the use of HI/I.sub.2 initiating systems to polymerize isopropenylphenyl glycidyl ethers. The use of CF.sub.3 SO.sub.3 H is shown to be ineffective.
It is difficult to predict which initiator/Lewis base combinations will result in a living cationic polymerization of a vinyl monomer. For example, S. Aoshima and T. Higashimura, op. cit., show that living polymerizations of 2-vinyloxyethyl benzoate and 2-vinyloxyethyl methacrylate monomers, where the ester functioning as a Lewis base is incorporated within its structure, can be conducted using EtAlCl.sub.2 but not with BF.sub.3 OEt.sub.2.
The present invention provides a process for the cationic polymerization of vinylic unsaturated compounds using a proton or carbenium or siliconium ion source, and/or Lewis acids; in combination with selected Lewis base.